Lifting magnet



May 30, 1939. H E HODGSON 2,160,019

LIFTING MAGNET Filed Oct. 22, 1937 Patented May 30, 1939 UNITED STATES PATENT OFFICE LIFTING MAGNET Application October 22, 1937, Serial No. 170,334

6 Claims.

This invention relates to improvements in electromagnets, and while not limited thereto is particularly applicable to lifting magnets.

Lifting magnets usually comprise a magnet frame having concentrically arranged inner and outer pole projections, a coil unit mounted in the space between the pole projections and an annular coil shield secured between the pole projections to form with the magnet frame a complete enclosure for the coil unit. In the patent to Howard E. Hodgson et al., No. 2,095,499, dated October 12, 1937, there is disclosed a lifting magnet of this type having a cast coil shield which is secured to the inner and outer pole projections 1 by continuous welded connections, the coil shield being of special form to facilitate welding thereof. Welded lifting magnets of the type disclosed in the aforementioned application have numerous advantages, but in some instances it has been 20 found that cast coil shields are defective and do not provide for proper sealing of the coil unit within the magnet frame.

The present invention has among its objects to provide a lifting magnet of the welded type 26 which overcomes the aforementioned objection.

Another object is to provide a lifting magnet having coil shielding means which is inexpensive and also of sturdy construction and which is particularly adapted for use in connection with 30 lifting magnets of large diameter.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be 35 described, it being understood that the embodiment illustrated is susceptible of modification without departing from the spirit and scope of the appended claims.

In the drawing,

40 Figure 1 is a vertical sectional view of a lifting magnet embodying the invention;

Fig. 2 is a fragmentary bottom view of the lifting magnet shown in Fig. l with the inner and outer pole shoes of the magnet removed, and

Figs. 3 and 4 are enlarged fragmentary sectional views of certain of the parts shown in Fig. 1.

Referring to Fig. 1, the same illustrates a lift- 50 ing magnet provided with a magnet frame I having a hollow cylindrical center pole projection 2 and an annular outer pole projection 3 on the under side thereof. A coil unit 4 is mounted in the annular space between the pole projec- 55 tions 2 and 3, and said unit comprises a core member 5 bored to fit over pole projection 2, an annular plate 6 mounted upon the upper end of said core member and a plurality of windings I mounted upon said core member, each of said windings being formed of strap material and be- 5 ing insulated in the usual manner.

Coil unit 4 is sealed within the space between pole projections 2 and 3 by an annular sealing disk 8 formed of sheet metal and having its inner edge secured to pole projection 2 by a con- 10 tinuous welded connection 9, and its outer edge secured to pole projection 3 by a. continuous welded connection [0. Coil unit 4 and sealing disk 8 are protected by a shield ll of annular form located between the pole projections 2 and 3 and held in place by inner and outer pole shoes 12 and I3 fixed to said pole projections.

More specifically, the upper face of sealing disk 8 engages the lower face of coil unit 4 and the inner edge of said disk is formed to provide a downwardly extending flange [4 while the outer edge thereof is formed to provide a downwardly extending flange i5. The inner flange [4 is of such diameter as to fit tightly around the inner pole projection 2 and the lower end of said pole pro- 2 jection is of reduced diameter to provide a shoulder 56 which is flush with the lower edge of said flange. The lower end of outer pole projection 3 is counterbored to provide a shoulder ll which forms an abutment for the outer marginal portion of sealing disk 8, and the outer flange 15 of said sealing disk is of such diameter as to fit tightly within said counterbore. Also the lower end of outer pole projection 3 is counterbored to provide a shoulder 58 which is flush with the lower edge of flange IS. The inner welded connection 9 extends between the lower edge of flange l4 and shoulder it on inner pole projection 2, while the outer welded connection it extends between the lower edge of flange I5 and shoulder I8 on outer pole projection 3. The flanges l4 and I5 render the marginal portions of the sealing disk relatively flexible to minimize strains on the welded connections 9 and I9, and welding of the sealing disk 8 to pole projections 2 and 3 insures proper sealing of coil unit 4 within the magnet frame I.

Shield ll comprises a casting of annular form having inner and outer portions 20 and 2| of increased thickness which are finished on opposite sides. Shield II is located between the flanges l4 and IS on sealing disk 8 and the inner and outer edges thereof are spaced from said flanges. However, the inner marginal portion of shield H extends below core member 5, while the outer marginal portion thereof extends below shoulder ll on outer pole projection 3. The lower face of coil shield ii is provided with radially arranged projections 22 which are V- shaped in cross section to eliminate cooling strains in the casting.

As hereinbefore stated, shield H is secured to the magnet frame by inner and outer pole shoes l2 and it. The inner pole shoe i2 is of circular form and is secured to inner pole projection 2 by bolts 23 passing through openings in said pole projection and having their heads countersunk 'in the lower face of said pole shoe. Inner pole shoe I2 is of such diameter as to engage the inner marginal portion 26 of shield H and the upper face of said pole shoe is provided with an annular flange 2 3 which is turned to fit within the opening in coil shield 3. Flange 2 1 is shouldered as shown at 25 to clear flange i i of sealing disk 8 and the welded connection 9, and the same is bored to fit the lower end of inner pole projection 2. The inner pole shoe l2 thus serves to hold shield l l in centered relation with respect to the magnet frame, and the arrangement is such that upon tightening of bolts 23 the inner marginal portion 28 of shield H and sealing disk 8 are clamped between said inner pole shoe and the lower end of core member 5. The outer pole shoe I3 is secured to an outwardly extending flange 26 on the lower end of outer pole projection 3 by bolts 2'! having their heads countersunk in the lower face of said outer pole shoe. Said outer pole shoe is provided with an upwardly extending peripheral flange 23 which is bored to receive the flange 26 on outer pole 3 and the inner marginal portion thereof is counterbored to receive the outer edge of shield l l and to provide a shoulder for engaging the under face of the marginal portion iii of said shield. Upon tightening of bolts 27 shield H and sealing disk 8 are clamped between the outer pole shoe l3 and the shoulder ll on outer pole projection 3. The channels on the upper face of shield it formed by the radial projections 22 are filled with a material such as concrete to provide rapid conduction of heat from the coil unit to shield ll Also the upper side of magnet frame I is provided with an opening 38 for receiving the terminals of coil unit l, one of said terminals being illustrated at 3|, and said terminals are each connected to an insulated terminal element 32. The terminal elements are located within a pocket 33 formed in the upper face of magnet frame and opening 353 is closed by a removable cover plate 34 while pocket is closed by a removable cover plate 35. The upper face of the magnet frame is also provided with the usual suspension lugs, one of which is illustrated at 36.

What I claim as new and desire to secure by Letters Patent is:

1. In a lifting magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections, an annular coil unit mounted in the space between said pole projections, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, continuous welded connections between said magnet frame and the inner and outer edges of said disk, and rigid supporting means engaging the under side of said sealing disk and supporting said disk substantially throughout to prevent flexing of any part thereof, said supporting means including a rigid shield of annular form secured to said inner and outer pole projections.

2. In a lifting magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections on the under side thereof, an annular coil unit mounted in the space between said pole projections, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, said sealing disk having a downwardly projecting flange formed on its outer edge tightly fitting within said outer pole projection and a downwardly projecting flange formed on its inner edge tightly fitting around said inner pole projection, continuous welded connections between the lower edges of said flanges and said magnet frame and rigid supporting means engaging the under side of said disk and supporting said disk substantially throughout to prevent flexing of any part thereof, said supporting means including a rigid shield of annular form secured to said inner and outer pole projections.

3. In a lifting magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections, an annular coil unit mounted in the space between said pole projections, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, continuous Welded connections between said magnet frame and the inner and outer edges of said disk, a rigid shield of annular form secured to said inner and outer pole projections, said shield having its upper face recessed to provide inner and outer flange projections which engage the under side of said sealing disk adjacent said welded connections and a filler of compacted material held within the recess in the upper face of said shield and engaging the under side of said sealing disk to prevent fiexing of the latter.

4. In a liftin magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections on the under side thereof, an annular coil unit mounted in the space between said pcle projections and having a core member bored to receive said inner pole projection, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, said outer pole projection being shouldered to provide an annular abutment for the outer marginal portion of said sealing disk, continuous welded connections between the inner and outer edges of said sealing disk and said inner and outer pole projections, and rigid supporting means engaging the under side of said disk and supporting said disk substantially throughout to prevent flexing of any part thereof, said supporting means in cluding a rigid shield of annular form secured to said inner and outer pole projections and engaging said sealing disk to clamp the same against the annular abutment on said outer pole projection and the lower end of said core member.

5. In a lifting magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections on the under side thereof, an annular coil unit mounted in the space between said pole projections, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, said sealing disk having downwardly extending circular flanges formed on the inner and outer edges thereof, continuous welded connections between the lower ends of said flanges and the inner and outer pole projections on said magnet frame, a rigid shield of annular form engaging the under side of said sealing disk, said disk having its upper face recessed to provide inner and outer flanges which engage said sealing disk adjacent said welded connections, pole shoes secured to said inner and outer. pole projections and engaging said shield to secure the same to said magnet frame and to clamp the same against the lower face of said sealing disk, and a filler of compacted material held within the recess in the upper face of said shield and engaging the under side of said sealing disk to prevent flexure of said sealing disk and to also provide for rapid conduction of heat from said coil unit to said shield.

6. In a lifting magnet, in combination, a magnet frame having concentrically arranged inner and outer pole projections, an annular coil unit mounted in the space between said pole projections, an annular sealing disk formed of thin sheet metal and mounted in the space between said pole projections to form with said magnet frame a complete enclosure for said coil unit, continuous Welded connections between said magnet frame and the inner and outer edges of said disk, a rigid shield of annular form engaging the under side of said sealing disk, said shield having radially arranged projections on the under side thereof which are V-shaped in cross section to provide radial channels in the upper face of said shield and a filler of compacted material between the lower face of said sealing disk and the upper face of said shield for preventing fiexure of any part of said sealingdisk and for also effecting rapid conduction of heat from said coil unit to said shield.

HOWARD E. HODGSON. 

